"setfenv" not setting the environment properly?

I've been playing around with environment manipulation, and ran into something that really stumbled me. When you try to index a nil value in an environment or table, it should invoke the __index metamethod (if one is set to it). However in my case, it's not doing that. Here's my code:

function Test(x)
	print(x) -- print's nil
end

setfenv(Test,setmetatable({},{
	__index=function(t,k)
		if(k=='x')then
			print("No '"..k.."' value exists, returning default...")
			return "Replaced with this string"
		else
			return getfenv()[k]
		end
	end
}))

Test() -- not assigning any parameters (so, "x" should be nil, therefore allowing "__index" to be invoked when the environment is indexed for "x", like in it's print function above).

Yet, the output still prints "nil". Can anyone help please? Is there any way I can use __index on this function without getting rid of it's argument?